Solid-state imaging devices which convert incident light into electric signals and output the electric signals as video signals have been known. Digital still cameras have also been known which display an image based on the video signals obtained from the solid-state imaging devices. In recent years, higher-resolution and higher-speed in transferring electric charges are required for cameras using the solid-state imaging devices, for further improving an image quality and functions.
In such solid-state imaging devices, thinning out pixels of which signal charges are read are proposed in order to improve the output speed of video signals. In addition, a method which reduces the number of pixels of output video signals by mixing a plurality of signal charges, and a method which improves the speed (frame rate) of outputting video signals by providing a plurality of rows (at least two rows) of horizontal transfer units are proposed (see Patent Literature 1, for example).
FIG. 8 is a plan view which illustrates an example of the configuration of a solid-state imaging device 400 in which a conventional charge coupled device (CCD) is used. This view shows an example of a two-row configuration of horizontal transfer units. The solid-state imaging device 400 includes a plurality of photoelectric conversion units PD arranged in a matrix in the vertical direction (downward in the diagram) and the horizontal direction (leftward in the diagram). In addition, vertical transfer units 430 which transfer, in the vertical direction, electric charges read from the photoelectric conversion units PD are provided beside the respective photoelectric conversion units PD.
A line memory LM which serves as a charge accumulation unit capable of temporarily accumulating the signal charges is connected to an end of each of the vertical transfer units 430. A first horizontal transfer unit 440a is connected to each of the line memory LM. In addition, a second horizontal transfer unit 440b is connected to the first horizontal transfer unit 440a with a horizontal internal transfer unit 450 being disposed in between. An output amplifier AMP1 which outputs the signal charges is provided at a horizontal end of the first horizontal transfer unit 440a, and an output amplifier AMP2 which outputs the signal charges is provided at a horizontal end of the second horizontal transfer unit 440b. 
In addition, a driving unit (not illustrated) is provided in the solid-state imaging device 400. The driving unit supplies a transfer driving pulse to each of the vertical transfer unit 430, the first horizontal transfer unit 440a, the second horizontal transfer unit 440b, and the horizontal internal transfer unit 450.